1. Field of the Invention
The invention relates to a sewing machine having a workpiece feed device having a feed dog which performs a lift and feed movement.
2. Background Information
A sewing machine is known from U.S. Pat. No. 4,674,426, wherein a rotating main shaft initiates the lift movement of a feed device and a pivotally driven oscillating shaft initiates the feed movement. In this case, a feed locus or orbit in the form of an ellipse flattened on one side, similar to the shape of an egg, is produced by reason of the described direct coupling of the oscillating shaft to the lift drive of the feed device. The feed locus or orbit does in fact render it possible to provide the feed drive with a transmission which is of a simple construction, but it does not allow for an optimum design of the vertical components of the feed locus or orbit, e.g. in an elliptical form.
An object of the invention is to develop further a workpiece feed device, in such a way that an optimum design of the vertical components of the feed locus or orbit of the feed dog and/or the feed device is possible.